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Messages - Matt Wilkinson

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Station Equipment Questions / Infrared thermal usb camera
« on: November 05, 2019, 11:36:55 AM »
At the recent Technical Workshop in Stuttgart, we heard from a number of people operating infrared cameras.  The reports were encouraging but the cameras are expensive. Could i ask what people on here think of these cheaper cameras?:
    Longwave infrared; 7.5 µm – 13.5 µm
    640 x 512
    12 µm pixel


Data and Software Questions / Re: CRDv2 experience (as a provider)
« on: October 07, 2019, 01:20:08 PM »
Please also see this earlier post on CRDv2.

I could not recover the author's name.  Was it you??

Data and Software Questions / CRDv2 experience (as a provider)
« on: October 07, 2019, 01:18:10 PM »
How are you getting on with generating version 2 CRD SLR data files?

At Herstmonceux, we are about to start submitting our data in CRDv2 format. I wrote a Python script to generate the files following a similar method to how we write the CRDv1 files in FORTRAN.

It wasn't too much trouble and i think it is all correct now. If you have not looked at doing this yet, there are changes to be aware of in some of the fields and there are also additional fields:
  • H5 Prediction Header
  • C5 Software Configuration
  • C6 Meteorological Instrumentation Configuration
  • C7 Calibration Target Configuration *new*
  • 41 Calibration Detail Record
  • 42 Calibration "Shot" Record *new*

One major change is the recording of the calibration records.  In the v2 version only one '40' record should be included with additional calibrations recorded as '41'.  The epoch of the '40' record should be the at the middle of the pass segment and the calibration value determined from pre and post measurements.

See the latest CRDv2 document from the ILRS website:

It was clear to me in doing this that more data can be included in the CRD files than we are providing at Herstmonceux.  In time, i will look at including the '30' records for Pointing angles.

We also don't collect the information requested in the '21' Meteorological Supplement Record. Is anyone collecting this information?:
  • Wind speed (m/s)
  • Wind direction (degrees azimuth, North is zero)
  • Weather conditions (two-digit SYNOP/WMO “present weather” code, or “rain”, “snow”, “fog”, “mist”, “clear”, “na”, etc.)
  • Visibility (km)
  • Sky clarity (i.e., zenith extinction coefficient)
  • Atmospheric seeing (arcsec)
  • Cloud cover (%)
  • Sky temperature in degrees Kelvin
We do however collect visibility values and so i will look in to including this in the future. Is there an instrument that anyone is using that reliably provides the rest of this information?

Please share your experience in providing CRDv2 below. Any questions or advice welcome


Mission Tracking Feedback / Recovered: Radioastron
« on: June 14, 2019, 02:18:14 PM »

Lavochkin Association did not manage to establish communication with the Spectr-R satellite. Attempts continued from 10 January to 30 May 2019. The State Commission examined the satellite’s technical condition on 30 May 2019 and decided to finish the RadioAstron observing program. The satellite successfully operated for 7.5 years instead of the originally planned 3 years. The link with the satellite was lost due to the very long exposure to the space radiation which has affected the onboard low-gain antenna communication system. Currently, the Astro Space Center is completing the data transfer, correlation and archiving of the vast amount of unique scientific data. International science teams continue to process, analyze and publish the results.

Open a Discussion / Recovered: 'Space debris EU-ESA agreement'
« on: June 14, 2019, 02:17:24 PM »
Good morning.
How is it going to affect our community this new in relation with space debris applications?

We are designing our new station in order to be compatible with space debris activities in the future if it is necessary.

In-Sky Safety / Re: FLARM
« on: June 14, 2019, 02:16:25 PM »
Recovered Post:

The TRX-1500 FLARM rx is not available any more. Another good option, the one we already acquired, is the AT-1 receiver (it is the TRX-1500 successor).

In-Sky Safety / Re: On telescope camera for plane spotting
« on: June 14, 2019, 02:15:56 PM »
Recovered post:

Good morning.
We are currently defining our Telescope system (our plan is to buy it this year). It is really interesting your work related with the optical camera for aircraft security. So we will have it into consideration for our system (in addition with ads-b, flarm, all-sky camera, directional microphone...).
Best regards.

Dear Laser Tracking Colleagues,

G'Day from Tokyo.

In the 21st International Workshop on Laser Ranging (conference site:, proceedings site:, I presented station-by-station performance charts (printed on 1-metre-long sheets) during the Clinic Session 3 co-hosted with Jose Rodriguez.  Here are the short summary of the analysis and the links to the charts.

Period: July 2017 to June 2018.
29 Stations with > 200 LAGEOS passes in the 1 year span.
More details about the analysis: See

Unlike the previous years' ones, this year's charts are organised PER STATION.  Matrix charts are also provided (printed on the reservse side) to help investigate the cause.

The first part contains:
  Residual wrt Range rate (negative in ascending (first) half, and positive in descending (second) half of a pass)
  Residual wrt Local time (defined by the station longitude, slightly different from the local standard time)
  Residual wrt Range rate (as specified in normal point data)
  Residual wrt Single-shot RMS (as specified in normal point data)
  Residual wrt Skew (as specified in normal point data)
  Residual wrt Kurtosis (as specified in normal point data)
  Residual wrt System delay (1), (2),.. (per system delay 'group')
  System delay (all sat) (including calibration data for other satellites not included in this analysis)
  System delay (A), (B), ... (vertical scale magnified as above)
  Calibration interval (cumulative) (typical calbration interval is at median (50%))

The matrix chart (second  part) labels, top-to-botumn = left-toright,  mean:
  Mon 17: Months from January 2017 (13 for January 2018)
  Hour: Local time
  # ret: Number of returns per NP bin
  Return rate
  RMS: Single-shot RMS
  Kurt: Kurtosis
  Range rate
  System delay (1), (2), ...
  O-C: POD residuals
7090 (Yarragadee),
7941 (Matera),
7825 (Mt Strolmo),
7237 (Changchun),
7105 (Greenbelt),
7810 (Zimmerwald),
7840 (Herstmonceux),
7110 (Monument Peak),
7501 (Hartebeesthoek),
7841 (Potsdam),
7821 (Shanghai),
8834 (Wettzell),
7839 (Graz),
7119 (Haleakala),
7819 (Kunming),
1887 (Baikonur),
7838 (Shimosato),
7249 (Beijing),
7827 (Wettzell),
7407 (Brasilia),
1873 (Simeiz),
1879 (Altay),
7845 (Grasse),
1893 (Katzively),
1891 (Irkutsk),
1868 (Komsomolsk-na-Amure),
1889 (Zelenchukskya),
1886 (Arkhyz),
7811 (Borowiec),

Best Regards,


Today, while writing my own CRD-parsing python3 code, I felt a little bit wheel-reinventing

Since the new CRD/CPF format is going to release at the Canberra meeting, I guess it's time to think about our new CRD2.0 python library?
It should have following functions: verify the CRD2.0 format, extract data, etc.

I found in GitHub the CRD/CPF library from Olli Wilkman:

Could be a good start.

Recover Post:

Hi Arttu

Water spraying over the laser electronics doesn't sound like fun!  :o

We run a Lauda E100 at the SGF. When we had temperature variation problems it wasn't  the water cooler temperature that was unstable it was the temperature control of the amp. That temperature control system became unstable as the water flow around it had become very low, sounds similar to your problem but not so bad.

The fix was to add a bottle of Durgol Universal Descaler, as recommended by Michael Schmidt, to the water and run it for 2+ hours. This restored the water flow rate meaning the amp temperature control could work as intended again so no more temperature variation to cause the range variation we'd seen.

We have run the same Lauda water cooler continuously since the arrival of our kHz laser so 10+ years. I have replaced the fan motor 2 or 3 times though, it's not impossible to get to but access is tricky.

The water cooler has always been set at 20°. We don't run a filter on the outlet as Michael told us to remove it, we also stopped using OptiShield on his advice. We have always changed the water at least once a year. Micheal now recommends changing the water and flushing the system with Durgol every 6 months.

The last time I changed the water I added a bottle of Durgol before draining the old water and noticed an obvious improvement in water flow, despite having used Durgol at previous changes. It appears it doesn't take long for the limescale build up inside the laser waterways to have a noticeable effect on flow rate.


Recovered Post:

Hi Arttu,
in Graz we are using (since delivery of the laser) a Lauda chiller. LAUDA ecoline RE110
Cooling power @20° = 500W; Heating power = 1500W;
We have a filter of 100µm at the output (renewing once a year). And we changed the position of the temperature sensor from internal (chiller reservoir) to the output tube of the laser for having shorter warm up times. As a “descaler” we are adding OptiShield to the distilled water. This mixture we are renewing around every 5 to 10 years but we have to add around half a litre of distilled water every week. (losing a lot ??) By the way, beside some very short service periods, we never switched the HQ-Laser system off.
Greetings, Franz

Recovered post:

I have a question especially for HighQ laser users (Matt, Sven, Franz et al.), what chiller are you using? Do you have some model from Lauda, with what specifications (cooling power, temperature stability; @Matt: how big deviations in temperature you had when you noticed the calibration changes?) We need to get a new one to replace our >10 year old Lauda in Metsähovi with a new one, and I'm trying to find the "best" option suited for our needs.

The backround is: we run into problems with the water cooling unit as we are not using our laser that much... even though the chiller has been on most of the idle time (and we have changed the water every once in a while), there was a major blockage inside the post amp. I had to use quite a lot of brute force, nasty chemicals and sharp tools to get the blockage open. Finally after this, everything went fine for some time until suddenly the water connector on the backside of the HighQ post amp analog modules broke down spraying the water all over the laser controller rack. Fortunately pretty much all of the electronics were shut down and everything seems to still work. Now finally the fan inside the cooling unit has stopped working (probably the motor is broken, pretty much impossible to replace) and the unit burnt two fuses while I was trying to operate the laser.

Lesson learned: be cautious and suspicious if you have water hoses connected on top of your electronics rack. Apparently it is the initial design from HighQ, seems that the connector was tightened too hard which had cracked the connector.


Lasers / Re: Polarisation
« on: June 07, 2018, 01:56:09 PM »
Hi Jens

The full story of our battle with polarisation in our system is here

Bottom line is that we were losing laser energy through our coudé path depending on the mirror position and we were losing > 50% of our return signal through a polarisation selective dichroic mirror.

The first thing you should do is establish if it is caused on the transmit or receive side. My favourite test was to point the telescope at the zenith and rotate in azimuth and record the intensity of the laser light backscatter at night. The polarisation state is preserved in the reflection by the small spherical water droplets in the atmosphere. We saw clear variation in intensity on both the transmission and reflection side of the dichroic but in opposite magnitudes.

If you've got polarisation problems, switching to circular will not solve this, but would take out the variation. We've not been successful in transmitting circular so would be interested to know how you get on.


Mission Tracking Feedback / Re: S-NET tracking
« on: June 04, 2018, 09:34:14 AM »
See the attached for a plot of kHz residuals from S-NET1 taken over the weekend at Herstmonceux SLR station

Lasers / Polarisation
« on: April 27, 2018, 10:28:09 AM »
We need to talk about polarisation!

At Herstmonceux, we are still emitting linear polarised laser light after an attempt to make it circular with a 1/4 wave plate failed. The circular polarisation was lost through the coudé mirrors before the beam left the emitter.

Would everyone please describe here the polarisation characteristics of their SLR systems.
  • What is polarisation state of the laser light emitted by your SLR system?
  • How are you achieving this?
  • Have you tested this and know that you are sending what you think you are at all telescope azimuths and elevations?
  • Can you control the emitted polarisation?
  • What are the polarising properties of your receive path [At Hx, we found our receive path to be highly selective to polarisation and we had to replace our dichroic mirror]
In the future, we plan to look further at circular polarisation and would be grateful for any advice from those that are able to send circular polarised light.  We also hope to return to looking at controlling the emitted linear polarisation orientation using a 1/2 wave plate.


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